Start by asking what the number measures
A headline about rising house prices is easy to remember. What it tells you about a particular house is a more careful question. A national or regional movement can help explain the market backdrop, but a property still has its own location, condition, accommodation and legal circumstances.
The CSO describes the Residential Property Price Index as a measure of changes in the average level of residential prices, adjusted for differences in the mix of properties sold (CSO, 2026). That adjustment matters: a month with more expensive types of homes changing hands is not automatically evidence that every comparable home has risen by the same amount.
An indexed estimate has assumptions
The CSO explains how a known earlier value can be updated using the ratio between two index readings. Its background notes describe the result as approximate and assume no material change in the dwelling or neighbourhood (CSO, 2024). It should be treated with that limitation in mind.
For a purely illustrative calculation, an earlier value of €200,000 multiplied by an index ratio of 1.10 produces €220,000. Those are invented figures to explain the arithmetic, not a valuation or a statement about today’s market. The multiplication cannot inspect an extension, identify a title issue or decide whether the earlier figure was reliable.
Return to the property and the evidence
For a home in Roscommon, Leitrim or Longford, ask which completed transactions are genuinely relevant and what is known about them. A nearby sale can still differ in size, condition, tenure or timing. An asking price is another kind of information and should be identified as such.
RICS guidance treats comparable evidence as information that needs scrutiny and analysis before it supports an opinion. It recognises that evidence varies in availability and quality (RICS, 2023). A useful explanation shows the reasoning between the transactions and the conclusion, rather than presenting a collection of prices as if they speak for themselves.
Use the release date and geography carefully
Keep the publication date separate from the period described by the data. Ask whether the series concerns all homes, a particular property type or a broader geographic area than the one you are considering. Where a figure is revised, retain the version used in an earlier report.
For a client, the helpful question is not simply “Have prices gone up?” It is “What evidence supports this opinion for this property, at this date?” Statistics can contribute to that answer without carrying more weight than they can reasonably bear.
References
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Central Statistics Office (CSO) (2026) Residential Property Price Index: methodology. Available at: Residential Property Price Index: methodology (Accessed: 1 November 2026).
Central Statistics Office (CSO) (2024) Residential Property Price Index March 2024: background notes. Available at: Residential Property Price Index March 2024: background notes (Accessed: 1 November 2026).
Royal Institution of Chartered Surveyors (RICS) (2023) Comparable evidence in real estate valuation. 1st edn, originally published 2019; reissued 2023. Available at: Comparable evidence in real estate valuation. 1st edn, originally published 2019; reissued 2023 (Accessed: 1 November 2026).
Further reading
Pirounakis, N.G. (2026) Real Estate Economics: A Point-to-Point Handbook. 2nd edn. Routledge. Edition, context & purchase links View / buy at publisher
Baum, A.E., Crosby, N. and Devaney, S. (2021) Property Investment Appraisal. 4th edn. Wiley-Blackwell. Edition, context & purchase links View / buy at publisher
Blackledge, M. (2017) Introducing Property Valuation. 2nd edn. Routledge. Edition, context & purchase links View / buy at publisher
Books listed for further reading have not necessarily been consulted in full. See the reading room for the basis of each recommendation.
General information for Irish property matters. The requirements of a particular instruction should be discussed with the appropriate professional. Editorial approach and source policy.
Put the guidance into practice
Explore the relevant service and what to prepareThe wider picture
Follow a guided reading route around this question.